Eccentric moving coil electrical



March 22, 219459. F. BARANOWSKL JR 2,465fi53 ECCENTRIC MOVING COIL ELECTRICAL METER 2 She e ts- Sheet 1 Filed Jan. 4, 1947 7%.. rev M w 0 tm ,L w X A .V///,/// L W l 4 1 H. 6% a 2 My r my W M F b L fgxmaq W W Z TWQ.

F. BARANOWSKI, JR 2,45,653

ECCENTRIC MOVING COIL ELECTRICAL METER Filed Jan. 4, 1947 2 Sheets-Sheet 2 Invntor: Frank Baranowski,Jr.

Hi5 Atofne t Patented Mar. 22, 1949 7 UNITED STATES PATENT forms ECCENTRIC MOVING COIL ELECTRICAL METER Frank Baranowski, Jr., Boston, Mass., assignor to General Electric Company, a corporation of New York Application January 4, 1947, Serial No. 720,279

creased, in an instrument which may use internal pivots and have a long scale.

My invention relates primarily to electrical measuring instruments of the permanent magnet field, direct current type which have a concentric air gap for one side of the moving coil across which the permanent magnet flux passes in a radial direction over a large portion of the arc of.

a circle, and sometimes designated concentric scale instruments. My invention concerns primarily the inner core structure and armature assembly, and another object is to provide a rugged internal pivot armature assembly unit which is easy to insert or withdraw from the field without disturbing the jeweled pivot adjustment.

In the usual prior art instrument of the general type to which my invention relates, a shaft usually extends througha central opening axially of the magnetic core and to which one side of the coil is secured, and with the pivots outside the ends of the coil. I depart from this arrangement. I use a coil the sides of which rotate in different circular gaps at different radii from the axis of rotation. The coil side of least radius ro- 6 Claims. (Cl. 171-95 tates in a gap across which no flux passes and the coil side of largest radius rotates in the flux gap. In one form of my invention the magnetic core is generally C-shaped and may be permanently fastened to the outer yoke and permanent magnet field structure. A plug of nonmagnetic material carrying internal pivots for the armature is removably inserted in the central opening of the C-shaped magnetic core with the armature coil completely assembled thereon, such plug containing the nonflux-carrying gap for the short side of the armature coil.

In another form of my invention the magnetic core and internal pivot support are made in one piece of magnetic material which is removable with the armature.

In either case the arrangement provides outer magnetic core and inner internal pivot supporting parts concentrically arranged and outer and inner coil gaps concentrically arranged, with only the outer gap carrying the active flux. The arrangement provides a better balanced and lighter armature assembly, a shorter axial instrument length, better protection for the instrument pivots, and more accessible lead-in spirals as compared 'to prior art instruments of the same general type.

The features of my invention which are believed to be. novel and patentable will be pointed out in the claims appended hereto. For a better understanding of my invention, reference is made in the following description to the accompanying drawings in which Fig. 1 represents a plan view of a permanent magnet field instrument with a removable internal pit ot plug and armature assembly in an instrument embodying my invention; Fig. 2 is a side view, partially in section, of the instrument of Fig. 1 with the armature coil pivoted therein; Fig. 3 is a plan view of a one-piece permanent magnetic field structure and core with a removable internally pivoted armature plug; Figs. 4 and 5 are plan and side sectional views of an internal pivot instrument embodying my invention having a removable inner magnetic core;

Fig. 6 is a view taken on line 66 of Fig. 5.

The instruments to be described are of the type in which only one side of the armature coil rotates in a flux air gap and is effective in producing torque. Heretofore such instruments have employed a shaft to which the idle side of the armature coil was secured. According to my invention the shaft is eliminated and the axial space heretofore used as shaft space is occupied by internal pivots for the armature. The idle side of the armature coil 'is somewhat removed from the axis of rotation and rotates in'an idle or fiuxless air gap of small radius as compared to the effective torque air gap in which the other side of the coil rotates. In such an arrangement the shaft and the coil supports and insulation heretofore used in securing the armature coil to the shaft are eliminated. The structure for pivoting, talancing and alignment of the armature is simplified and reduced in size, weight, and cost and is somewhat more compact and rugged as compared to previous arrangements. In my invention the idle side of the coil helps to balance rather than contributing to unbalance of the armature, so that less counterbalancing is required and an exceptionally high ratio of torque circular and extends through an arc of some 800 degrees. A soft iron yoke 4 is secured to the outer i also of magnetic material. The outer circular surface of the inner core defines the other or inner side of the circular air gap 3. This magnetic field is formed in one integral structure as by cast welding the pole shoe 2, yoke 4, tongue I, and core 8 to the permanent magnet. It is practical to form the tongue I and inner core 8 of powdered, sintered magnetic material. The permanent magnet is polarized after assembly of the integral structure and no keeper or other precaution is necessary to prevent demagnetization, as no appreciable change of material in the air gap or reluctance to the flow of magnetic flux path crossing such gap can occur. Along one radius of the inner core a slot 1 is provided forthe purpose of inserting one side of an armature coil through this opening. The slot I may be adjacent either side of the tongue 5 or in a zero center scale instrument. it maybe directly opposite the tongue. After the armature coil is in place the slot I may be filled up. if desired, with a plug of magnetic material as shown at 42, Fig. 3, although this is not essential when the slot comes at one end of the air gap.

The armature coil l gis rotativeiy supported in a die cast frame II which need not be of magnetic material. The frame III is in the form of a plug having a cylindrical outer surface of a siz to fit snugly into the cylindrical opening in. the c-shaped core I. Frame II contains a radial slot Ii communicating with a C-shaped air gap represented as made in two parts 3| and I2 fasspace l2 for inserting and accommodating one.

side of the armature coil 0 therein. The plug or frame I 0 also contains a hollow core part I! secured to the outer shell part by a tongue l4. The frame it is provided with lateral extensions or tabs ii at its top which, when the frame is inserted in place in the core as represented in Figs. 1 and 2, rests against the top of core part 6 and so that the frame may be fastenedjn place by screws II. The core part II of the frame Ill contains an axial bore II for the purpose of holding jewel plugs It and ll for rotatively supporting the armature coil 8 on internalpivots 20 and 2| as best shown in Fig. 2. The upper Jewel it is immovably secured in the plug part it, while th lower jewel may slide freely in the bore hole I! unless held in place by-a set screw 22. Between the jewels in the bore I1 is a light compression spring 23. The lower jewel may then be adjustable in the bore and, when properly adjusted,

secured in place by the small set screw 22 which is contained in a threaded radial opening in the lower end of tongue part l4.

The armature coil I is pivoted on an axis which is central or concentric with respect to the plug 4 I and I4 are on opposite sides of the axis of rotation as are the long and short sides of the coil 2, thus permitting maximum rotation of the armature. It is evident that the arrangement permits the elimination of an armature shaft. The internal pivots shorten 'the axial length of the armature by the amount which such jewels and pivots would occupy if placed outside the armature. The armature coil is more nearly balanced than is the case where one side is placed next to the shaft and axis of rotation, so that less counterweight balancing is required. The long side 24 of the coil is preferably placed on the opposite side of the axis of rotation from the pointer which is shown at 2! and is secured to the top end of the coil 0, and helps to balance the weight of the coil about the axis of rotation. As a result only relatively small adjustable counterwelghts indicated at 24, 21, and 2| are required.

The weight indicated at 28 is made of a moisture absorbent material designed to absorb and give up moisture in the same relation as thatof the armature'coll I,- so as to maintain perfect balance under differentwhumidity conditions. The lead-in spirals llaand Iffor the armature coil have their inner ends secured in fixed relation to th jouter ends of the coils near the axis of rotation; The disposition and accessibility of these'lead-in'spirals are no longer encumbered by external pivots and shaft extensions. The outer or normally stationary ends of the lead-in spirals are secured by a removable framework tenedtogethter by screws. The part II is 'secured by screws at 34 to the outer tongue portion of the magnetic circuit and has a lower arm 25 extending toward the axis of rotation to support the outer end of lead-in spiral It on 'a limb in a manner to permit initial rotary adjustment of such spiral.

The upper frame part 32 has a hollow circular part which extends around the axis of rotation and an inwardly extending tongue part 33 which I supports a hub 31 on which the outer end of upframe l'l, its air gap space I: and the air gap 3,

and the radii of its long and short sides designated 24' and 2441 are the same as the mean radius of the gaps 3 and i2, such that the side 24 rotates freely in the outer magnetic gap 3 and the 'side 24a rotates freely in the idle or nonmagnetic gap l2. It is noted that rotation of the long side of th coil is limited to an angle of about 300 degrees by the tongue part 5, and that the short side of the coil is limited in rotation to the same 300 degrees by the tongue part 14. As pictured in Figs. 1 and 2, the coil 9 is at the center point of its rangeof rotation and may rotate about 150 degrees in either direction by per spiral 29 is rotatively secured. Linked with the rotary member of this spiral support is a crank arm a pivoted on ahub at I. to serve as a zero adjustment device for the pointer. A scale plate is secured above and in spaced relation to the field magnet as by means of studs and screws one of which is represented at 4! in Fig. 1. Other bolts may be provided through the field structure for mounting the instrument as desired.

When a magnetic plug such as shown at 42, Fig. 3, is used to close the gap at I, the magnet will be polarized with the plug in place. It is evident that the field fiux path is in general the same as in prior center core, concentric gap, permanent magnet field direct current instru-' ments and crosses the active fiux gap 3 in a radial direction over an arc of some 300 degrees at a uniform density if the air gap is made uniform. Special scale distributions may make it desirable to use an air gap which varies from uniformity. The field flux enters the central magnetic core 6 through the tongue part at ii.

In assembling the instrument the armature is first assembled on its plug it while removed from the field structure. This is done by first assembling and positioning the jewels It and II in the bore of plug it. The coil frame with its coil. pivots, balance weights, pointer and lead-in connections, is then assembled on the plug by first reason of the fact that the radial tongue parts passing the short side 24:: of the coil through the aceaoce 1 I gap at i2 and then orienting the coil until its pivots are in line with the jewels. The screw 22 is loosened to allow the spring 23 to push jewel l6 outward until the proper pivot pressure is obtained with the pivots 20 and 2| seated in their jewels f8 and I9. Screw 22 is then tightened.

This armature may be approximately balanced plug is then moved endwise into place and the screws 16 are put in and tightened. The frame parts 86 and 32 with the parts carried thereby are then added. The spirals 29 and 36 are then -connected at their outer ends to the crank arms for that p rp se carried by the. hubs such as 31. The spirals are then rotatively adjusted to position the instrument at approximately the zero scale position and are connected up with the circuit which is to energize the armature coil. The scale plate is added and th pointer set on zero with the zero set 38. A final adjustment for armature balance is made if necessary.

Inthe operation of the instrument only the long side of the coil moves in a fiux gap 3, as there is no fiux in the inner concentric gap l2. The operation is otherwise the same as for instruments having a coil side next to the shaft on the axis of rotation.

The armature assembly plug arrangement represented in Fig. 3 is the saine as that explained a in connection with Figs. 1 and 2 and is shown stripped of many of the instrument parts to more clearly indicate the important novel features;

Figs. 4, 5, and 6 represent another embodiment of my invention which differs primarily from the instrument previously explained by employing a removable inner magnetic coreand internal pivot support made in one piece of magnetic material separable from the remainder of the magnetic circuit. This structure is best shown in Figs. 5 and 6 and comprises the outer c-shaped core part 6 a side 24a is passed through gap 4! edgewise and the coil 8 is turned to the position shownin the drawing and then mounted on its jewels in the same manner as explained in connection with Fig. 2. Core 42 is then secured to the frame composed of parts 46 and 32, and the spirals are connected up and adjusted before these parts are inserted into the field structure. Then the frame with the armature assembly thereon is inserted into place in the field structure and bolted in place by the bolts 46. While in Figs. 5 and 6 the inner jewel support 43 is generally made of magnetic material, there is no tendency for flux l0 modifications within the true spirit and scope Letters Patent of the United States is:

1. An electrical measuring instrument comprising a field magnet including a O-shaped magnetic part, a circular outer magnetic part united to the outer surface of the O-shaped part and with a tongue of magnetic material extending radially inwardwithin the opening in the C-shaped part, and a magnetic core part within the C-shaped part and magnetically united with the tongue part, the inner surface of the c-shaped part and .the outer surface of the core part defining a circular air gapof the order of 300 degrees in arc length, at least a portion of said field magnet being made of permanent magnet-material and po- '62 which corresponds to part 6 of Fig. 3, the

inner internal pivot support part 43 which corresponds to part l3 of Fig.3, and the tongue part '64 which corresponds to part l4 of Fig. 3. The

gap for inserting the short side 24a of the coil 9 into the inner gap I2 is provided at 45 before the core is secured to a frame part 46 by screws 4'l.-

contact with the tongue 5 of the permanent magnet field structure and to correctly position the iarized to produce flux across said gap, said core part having an interior circular opening and a bearing support centrally within'said opening positioned in place by a tongue secured between it and the core part on a radius diametrically opposite to that of the previously mentioned tongue of magnetic material, said structure providing an inner circular air gap about the'bearing support concentric with the first-mentioned air gap and of approximately the same arc length, and an sides thereof in said respective air gaps.

core part 42 concentric with the inner pole shoe I 2 of the field structure. The gap 45 and spacer lugs 48 areon the opposite side of the axis of rotation from the inner tongue 44 and are symmetrical with respect to the center line of such tongues. The frame part 46 is held in place by bolts 49 passing through holes in the tongue 5.

' thereon are assembled in core part 43 before this part is fastened to frame part 46. The short coil p 2. An electrical measuring instrument comprising a field magnet including a O-shaped magnetic part. a circular outer magnetic part united to the outer surface of the C-shaped part and with a tongue of magnetic material extending radially inward within the opening in the C-shaped part, and a magnetic; core part within the c-shaped part and magnetically united with the tongue part, the inner surface of the C-shaped part and the outer surface of the core part defining a circular air gapof the order ,of 300 degrees in arc length, at least a portion of said field magnet being made of permanent magnet material and poiarized to produce flux across said gap, said core part having an interior circular opening and a bearing support centrally within said opening positioned in place by a tongue secured between it and the core part on a radius diametrically opposite to that of the previously mentioned tongue of magnetic material, said structure providing an inner circular air gap about the bearing support concentric with the first-mentioned air gap and of approximately the same arc length, and an armature coil having internal pivots mounted for rotation in said bearing support with opposite coil sides thereof in said respective air gaps, said core part having aradial opening to permit passage of a side of the coil therethroughduring assembly.

3. An electrical measuring instrument,compris-- faces of the C-shaped and core parts defining a circular air gap extending over an are greater than 180 degrees, at least a portion of said magnetic circuit being of permanent magnetic matea rial and polarized to produce a fiux across said air gap, said core part having an interior circular opening and a bearing support centrally within said opening secured in place by a tongue between it and the core on a radius diametrically opposite to that of said previously mentioned tongue, said tongue and bearing support being formed integral with said core part and of the same material, said structure forming an inner circular air gap about the bearing support concentric with saidfirst-mentioned gap and of approximately the same arc length, and an armature coil having internal pivots mounted for rotation in said hearing support on an axis concentric with said air gaps, said coil having one side in the first-mentioned gap and the other side in the second-mentioned gap, said core having a radial gap adjacent the point where united to the first-mentioned magnetic tongue to permit a side of said coil to be passed therethrough into the inner air gap during assembly when said core part is removed from remainder of the magnetic field.

4. An electrical measuring instrument compris- 5. An electrical measuring instrument having inner and outer concentric air gaps, each of an arc length of theorder of 300 degrees, a magnetic circuit for producing a flux across the outer gap, said magnetic circuit having inner and outer pole piece portions which define the outer gap,

.-an armature including a coil pivoted for rotation on an axis concentric with said air gaps, and with one of its coil sides in the outer gap and its other coil side in the inner gap, a bearing support within said coil on the axis of rotation thereof, and on which said coilis rotatively supported, supporting structure for the bearing support and portion of a the magnetic circuit contained within said coil which supporting structure includes a radial to ue Portion defining the length of the outer gap and a second radial tongue portion defining the length of the inner gap, said radial tongue portions being positioned on diametrically opposite sides of the axis of rotation of the coil so as to obtain the maximum free arc of rotation for said coil, said armature, bearing support, and at least a portion of said supporting structure being removable as a unit from within the outerpole piece portion of said magnetic circuit.

6. An electrical measuring instrument having a magnetic circuit comprising a c-shaped part, a hollow cylindrical core part within the C-shaped part and an outer circular yoke and a radial tongue part joining the c-shaped part to the 'core part, a circular air gap of the order or. 300 degrees between the C-shaped and cylindrical core parts, at least a portion of said magnetic circuit being 0! permanent magnet material and polarized to produce a flux across said air gap, an armature ing an inner cylindrical core, an outer magnetic yoke having a radially inwardly projecting magnetic to e united to the core and a c-shaped magnetic part between the core and yoke but separated from the core to provide a circular air gap between the inner surface of the c-shaped part and the outer surface of the core, a considerable portion of said c-shaped part being of perj manent magnet material and polarized radially to produce a flux across said gap, said cylindrical core being hollow, a removable plug fitted into said hollow core. said plug having an outer cylindrical shell and an inner central bearing support joined to the shell by a radial tongue, said plug thus containing an inner circular air gap concentric with the first-mentioned air gap, said gaps extending over arcs of the order of 300 degrees length, means for securing said plug in said core with its tongue diametrically opposite to the first-mentioned magnetic tongue, and an armature coil surrounding the bearing support portion of said plug and rotatively supported thereon on an axis concentric with said gaps and with one side of the coil in the outer flux air gap and the other side of the coil in the inner air gap, said core and shell of said plug having radial slits therein for the purpose of passing one side of the coil therethrough.

to that of the radial tongue part of the magnetic circuit, said core part and rotatively mounted armature being removable from within the remainder of the magnetic circuit and said core part having a radial opening adjacent the point where it joins with the remainder of the ma'lnetic circuit for the purpose of permitting one side of the coil to be passed therethrough.

FRANK BARANOWSKI, J!-

E REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,623 Hickok Mar. 27, 1945 2,394,113 Seaver et al. Feb. 5, 1948 FOREIGN pa'rmvrs Number Country Date 112,990 Great Britain Feb. .4, 1918 

